1. Statement of the Technical Field
The inventive arrangements relate generally to slot antennas, and more particularly to tapered slot patch antennas.
2. Description of the Related Art
Patch antennas are very popular due to their compact planar configuration. In its simplest form, a microstrip patch antenna consists of a radiating patch on one side of a dielectric substrate, which has a ground plane on the other side. Despite the relatively narrow bandwidth of many patch antenna designs, they are well suited for many applications. Various modifications can be included in patch antennas to increase their overall bandwidth. One such broadband antenna design is the bow-tie antenna that consists of two triangular patches that are fed either through a pair of microstrip lines on their surface or by lines originating on different conductor layers.
Printed slot antennas comprise a slot in the ground plane of a grounded substrate. The shape of the slot can be selected so to conform to the shape of many designs normally associated with common microstrip patch antennas. For example, conventional slot antenna designs include rectangular slots, annular slots, and tapered slots. Slot antennas are generally bidirectional radiators. They radiate electromagnetic energy in opposing sides of the surface in which the slot is formed. Radiation in a single direction is commonly achieved by using a reflector plate on one side of the slot. Microstrip slot antennas are advantageous in that they can potentially offer bandwidths that are somewhat larger as compared to ordinary patch antennas.
Tapered slot antennas are also known in the art. For example, U.S. Pat. No. 6,429,819 to Bishop, et al. discloses a dual band bow-tie shaped slot antenna. Bow-tie antennas are also discussed in an article entitled Center-Fed Microstrip Patch Antenna, Zhi Ning Chen and Michael Yan Wah Chia, IEEE Transactions on Antennas and Propagation, Vol. 51, No. 3, March 2003, p. 483. The bow-tie shaped slot antenna generally consists of two triangular shaped slot elements which converge at the points of the triangles to form a narrow gap. The bow-tie shaped slot is etched into a conductive patch surface. The two bands are fed with a single antenna feed attached across a gap between the midpoints of the converging region of the bow-tie segments. Alternative feeds are known in the art. The low band frequency of operation in such an antenna is defined by a dimension of the conductive surface in which the slot is etched. The higher band frequency of operation is primarily determined by the dimensions of the bowtie slot.
Although the bow-tie slot antenna is relatively compact, there is a continuing demand for devices that offer multi-band performance in smaller packages. Further, there is a continuing need for antennas of this type that offer high gain on multiple frequency bands while providing similar radiation patterns at the two different frequency bands. Providing all of these characteristics in a very compact package can be a challenging problem.